Enable developer option and enable Force 4x MSSA option for a better gaming experience, uninstall unwanted apps, disable background services and also use RAM cleaner to optimize the device
One thing you gotta know is that your phone reduce cpu speed if it's too warm, it's called cpu throttling. If your phone is rooted, there's some softwares that can overclock your phone processor in order to gain some fps, 10 to 20 % improvement.
By example: